Apparatus employing semi-permeable membranes are employed for various purposes. They are used, for example, in reverse osmosis processes to separate components of a fluid mixture. They are also used in electrode apparatus for the detection and measurement of specific components in a fluid mixture.
One apparatus, for example, previously suggested for the detection and measurement of glucose in body fluids, such as blood, consisted of a sample chamber into which samples were introduced in discrete individual amounts. One side of a semi-permeable membrane containing glucose oxidase was in communication with the same chamber and was capable of allowing portions of the sample in the chamber to pass therethrough. During this passage the glucose oxidase in the membrane catalyzed the oxidation of the glucose in the presence of oxygen in the sample to form hydrogen peroxide. A polarographic anode-cathode assembly was positioned in close proximity to the other side of the membrane and was capable of measuring the amount of hydrogen peroxide formed, thus detecting and measuring the amount of glucose in the sample.
This prior art apparatus had several disadvantages. First, when attempts were made to miniaturize the apparatus, the means for mounting the membrane against the polarographic electrode assembly often caused undesirable rupture of the membrane during mounting or subsequent use. Second, there was often an undesirable slowness in electrode response due to variations in membrane mounting and due to fluids, such as gases, being trapped between the membrane and the electrode assembly. The prior art apparatus was also not capable of handling continuous sampling conditions.
These and other disadvantages of the prior art membrane apparaus are overcome by the apparatus of the present invention.